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Toward the modeling of mucus draining from human lung: role of airways deformation on air-mucus interaction.

Mauroy B, Flaud P, Pelca D, Fausser C, Merckx J, Mitchell BR - Front Physiol (2015)

Bottom Line: Moreover, the higher the pressure or the quicker it is applied, the higher is the air flow and thus the mobilization of secretions.Generally, the first effects of manipulations is a decrease of the airway tree hydrodynamic resistance, thus improving ventilation even if secretions do not get out of the lungs.Finally, we propose and tested two a dimensional numbers that depend on lung properties and that allow to measure the efficiency and comfort of a manipulation.

View Article: PubMed Central - PubMed

Affiliation: Laboratoire J. A. Dieudonnée - UMR CNRS 7351, Université de Nice-Sophia Antipolis Nice, France.

ABSTRACT
Chest physiotherapy is an empirical technique used to help secretions to get out of the lung whenever stagnation occurs. Although commonly used, little is known about the inner mechanisms of chest physiotherapy and controversies about its use are coming out regularly. Thus, a scientific validation of chest physiotherapy is needed to evaluate its effects on secretions. We setup a quasi-static numerical model of chest physiotherapy based on thorax and lung physiology and on their respective biophysics. We modeled the lung with an idealized deformable symmetric bifurcating tree. Bronchi and their inner fluids mechanics are assumed axisymmetric. Static data from the literature is used to build a model for the lung's mechanics. Secretions motion is the consequence of the shear constraints apply by the air flow. The input of the model is the pressure on the chest wall at each time, and the output is the bronchi geometry and air and secretions properties. In the limit of our model, we mimicked manual and mechanical chest physiotherapy techniques. We show that for secretions to move, air flow has to be high enough to overcome secretion resistance to motion. Moreover, the higher the pressure or the quicker it is applied, the higher is the air flow and thus the mobilization of secretions. However, pressures too high are efficient up to a point where airways compressions prevents air flow to increase any further. Generally, the first effects of manipulations is a decrease of the airway tree hydrodynamic resistance, thus improving ventilation even if secretions do not get out of the lungs. Also, some secretions might be pushed deeper into the lungs; this effect is stronger for high pressures and for mechanical chest physiotherapy. Finally, we propose and tested two a dimensional numbers that depend on lung properties and that allow to measure the efficiency and comfort of a manipulation.

No MeSH data available.


Role of oscillating pressure Po, with Ps = 0.6 cmH2O and f = 20 Hz, data computed at the end of the manipulations for time t = 230s. (A) Volume of mucus getting out of the tree. (B) Relative hydrodynamic resistance of the tree. (C) Mean mucus position in the tree, in generation index. The red dashed line represents the value before the manipulation.
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Figure 10: Role of oscillating pressure Po, with Ps = 0.6 cmH2O and f = 20 Hz, data computed at the end of the manipulations for time t = 230s. (A) Volume of mucus getting out of the tree. (B) Relative hydrodynamic resistance of the tree. (C) Mean mucus position in the tree, in generation index. The red dashed line represents the value before the manipulation.

Mentions: We investigated first the role of the oscillating pressure Po. Because static pressure has only a small effect in our model, we assume Ps = 0.6 cmH2O which makes the total pressure applied on the thorax oscillate between 0 and 1.2 cmH2O. The frequency f is kept at 20 Hz. As predicted, the larger the amplitude of the oscillations, the more efficient is the manipulation, see Figure 10. As before, a more efficient mechanical manipulation tends to send more mucus down the tree, as shown on Figure 10C, because oscillations are symmetric and applied during the whole cycle of ventilation.


Toward the modeling of mucus draining from human lung: role of airways deformation on air-mucus interaction.

Mauroy B, Flaud P, Pelca D, Fausser C, Merckx J, Mitchell BR - Front Physiol (2015)

Role of oscillating pressure Po, with Ps = 0.6 cmH2O and f = 20 Hz, data computed at the end of the manipulations for time t = 230s. (A) Volume of mucus getting out of the tree. (B) Relative hydrodynamic resistance of the tree. (C) Mean mucus position in the tree, in generation index. The red dashed line represents the value before the manipulation.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4525672&req=5

Figure 10: Role of oscillating pressure Po, with Ps = 0.6 cmH2O and f = 20 Hz, data computed at the end of the manipulations for time t = 230s. (A) Volume of mucus getting out of the tree. (B) Relative hydrodynamic resistance of the tree. (C) Mean mucus position in the tree, in generation index. The red dashed line represents the value before the manipulation.
Mentions: We investigated first the role of the oscillating pressure Po. Because static pressure has only a small effect in our model, we assume Ps = 0.6 cmH2O which makes the total pressure applied on the thorax oscillate between 0 and 1.2 cmH2O. The frequency f is kept at 20 Hz. As predicted, the larger the amplitude of the oscillations, the more efficient is the manipulation, see Figure 10. As before, a more efficient mechanical manipulation tends to send more mucus down the tree, as shown on Figure 10C, because oscillations are symmetric and applied during the whole cycle of ventilation.

Bottom Line: Moreover, the higher the pressure or the quicker it is applied, the higher is the air flow and thus the mobilization of secretions.Generally, the first effects of manipulations is a decrease of the airway tree hydrodynamic resistance, thus improving ventilation even if secretions do not get out of the lungs.Finally, we propose and tested two a dimensional numbers that depend on lung properties and that allow to measure the efficiency and comfort of a manipulation.

View Article: PubMed Central - PubMed

Affiliation: Laboratoire J. A. Dieudonnée - UMR CNRS 7351, Université de Nice-Sophia Antipolis Nice, France.

ABSTRACT
Chest physiotherapy is an empirical technique used to help secretions to get out of the lung whenever stagnation occurs. Although commonly used, little is known about the inner mechanisms of chest physiotherapy and controversies about its use are coming out regularly. Thus, a scientific validation of chest physiotherapy is needed to evaluate its effects on secretions. We setup a quasi-static numerical model of chest physiotherapy based on thorax and lung physiology and on their respective biophysics. We modeled the lung with an idealized deformable symmetric bifurcating tree. Bronchi and their inner fluids mechanics are assumed axisymmetric. Static data from the literature is used to build a model for the lung's mechanics. Secretions motion is the consequence of the shear constraints apply by the air flow. The input of the model is the pressure on the chest wall at each time, and the output is the bronchi geometry and air and secretions properties. In the limit of our model, we mimicked manual and mechanical chest physiotherapy techniques. We show that for secretions to move, air flow has to be high enough to overcome secretion resistance to motion. Moreover, the higher the pressure or the quicker it is applied, the higher is the air flow and thus the mobilization of secretions. However, pressures too high are efficient up to a point where airways compressions prevents air flow to increase any further. Generally, the first effects of manipulations is a decrease of the airway tree hydrodynamic resistance, thus improving ventilation even if secretions do not get out of the lungs. Also, some secretions might be pushed deeper into the lungs; this effect is stronger for high pressures and for mechanical chest physiotherapy. Finally, we propose and tested two a dimensional numbers that depend on lung properties and that allow to measure the efficiency and comfort of a manipulation.

No MeSH data available.